Engine crack that grounded F-35 traced to thermal creep 06 Mar 2013 Zach Rosenberg
Engine crack that grounded F-35 traced to thermal creep
"Bennett Croswell, president of Pratt & Whitney's military engine division, says a problem with F135 engines that grounded the Lockheed Martin F-35 is due to thermal creep, and is unlikely to affect the aircraft further as it returns to flight status.
The issue was a crack in a third-stage turbine blade on a single engine. As a precaution, the US military grounded all F-35 aircraft until a cause was discovered.
"During [an] inspection we found about 1/6-inch (4.2mm) crack on the turbine blade," says Croswell. "We felt we could continue to fly, and we took that recommendation to the (joint programme office), but on consultation with them we both came to the conclusion it was safer to suspend operations."
Thermal creep from high-temperature, high-intensity testing was found to be the cause of the crack. The engine the tenth engine built, powers the second F-35A, was tested extensively at supersonic speeds and low altitudes, generating significant more heat than expected.
"It was operating at levels 4X an operational mission, and 4X of levels we had qualified the engine for," says Croswell. "That was very good news, you don't want something like high-cycle fatigue or low-cycle fatigue." The issue is not expected to impact operational aircraft for months or years, depending on how the aircraft are flown...."